vision

Neuroscientists at Emory University have found that people who experience a mixing of the senses, known as synesthesia, are more sensitive to associations everyone has between the sounds of words and visual shapes. The results are published in the European Journal of Neuroscience.

Synesthesia is a stable trait, and estimated to be present in 1 to 4 percent of people. It can be inherited, although the precise genes have not been identified. One of the most common forms of synesthesia is when people involuntarily see particular colors in connection with letters, numbers or sounds.

Many artists and composers have described their experiences with synesthesia. Children with synesthesia say sometimes that it is distracting when they are trying to read. Thus, understanding the origins of synesthesia may help people with dyslexia or other learning differences, or people who have lost their sight or hearing and are trying to engage in sensory substitution for rehabilitation.

Researchers led by neurologist Krish Sathian, MD, PhD, recruited 17 people with synesthesia, and asked them to take a form of the IAT (implicit association test). Known for its use probing social attitudes such as racial prejudice, the IAT can also assess “cross-modal correspondences.”

An example of a cross-modal correspondence is that we describe musical notes as being “high” or “low” – words that also signify relative positions in space. Another is that we think of some sounds such as “m” and “l” as soft, and are more likely to associate them with rounded shapes. Similarly, we connect hard sounds such as “k” and “t” with angular shapes.

“There’s been a debate about synesthesia,” Sathian says. “Are the associations synesthetes have just extreme versions of cross-modal correspondences that other people have, or are they qualitatively different?”

Sathian and his colleagues found that people with synesthesia were more sensitive to correspondences between the sounds of pseudowords — words without meaning in English — and rounded or angular shapes. Read more

Congratulations to John O’Keefe, May-Britt Moser and Edvard Moser for receiving the 2014 Nobel Prize in Medicine. The prize is for discovering “the brain’s navigation system”: place cells, cells in the hippocampus which are active whenever a rat is in a particular place, and grid cells, cells in the entorhinal cortex which are active when the animal is at multiple locations in a grid pattern.

Former Yerkes researcher Beth Buffalo and herÂ graduate studentÂ Nathan KillianÂ were the first to directly detect, via electrode recordings, grid cells in the brains of non-human primates. Buffalo is now at the University of WashingtonÂ and Killian is at Harvard Medical School.

A significant difference about theirÂ experiments was that theyÂ could identify grid cellsÂ when monkeys were moving their eyes, suggesting that primates don’t have to actually visit a place to construct the same kind of mental map. Another aspect of grid cells in non-human primates not previously seen with rodents is that the cells’ responses change when monkeys are seeing an image for the second time.

Following that report, grid cells were also directlyÂ detected inÂ human epilepsy patients. The Mosers themselves notedÂ in a 2014Â review, “It will be interesting to see whether the same cells that respond to visual movement in monkeys also respond to locomotion, or whether there is a separate system of grid cells that is responsive to locomotion.”

Dopamine-restoring drugs already used to treat Parkinsonâ€™s disease may also be beneficial for the treatment of diabetic retinopathy, a leading cause of blindness in adults, researchers have discovered. The results were published recently in Journal of Neuroscience.

Diabetic retinopathy affects more than a quarter of adults with diabetes and threatens the vision of more than 600,000 people in the United States. Doctors had previously thought most of the impairment of vision in diabetic retinopathy came from damage to the blood vessels induced by high blood sugar, but had known that dopamine, a vital neurotransmitter in the brain, was also important in the retina.

â€œThere was some evidence already that dopamine levels were reduced in diabetic retinopathy, but whatâ€™s new here is: we can restore dopamine levels and improve visual Ray Ban outlet function in an animal model of diabetes,â€ says Machelle Pardue, PhD, associate professor of ophthalmology at Emory University School of Medicine and research career scientist at the Atlanta VA Medical Center. Read more

When processing what the eyes see, the brains of primates don’t use square grids, but instead use triangles, research from Yerkes neuroscientist Beth Buffalo’s lab suggests.

Elizabeth Buffalo, PhD

She and graduate student Nathan Killian recently published (in Nature) their description of grid cells, neurons in the entorhinal cortex that fire when the eyes focus on particular locations.

Their findings broaden our understanding of how visual information makes its way into memory. It also helps us grasp why deterioration of the entorhinal cortex, a region of the brain often affected early by Alzheimer’s disease, produces disorientation.

The amazing thing about grid cells is that the multiple place fields are in precise geometric relation to each other and form a tessellated array of equilateral triangles, a â€˜gridâ€™ that tiles the entire environment. A spatial autocorrelation of the grid field map produces a hexagonal structure, with 60Âº rotational symmetry. In 2008, grid cells were identified Gafas Ray Ban outlet in mice, in bats in 2011, and now our work has shown that grid cells are also present in the primate brain.

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Grid cells fire at different rates depending on where the eyes are focused. Mapping that activity across the visual field produces triangular patterns.

The project is being led by Emory pediatric rheumatologist Sheila Angeles-Han, MD, MSc. Han recently received a $40,000 grant from the Knights Templar Eye Foundation to augment her work in this area. She is collaborating with pediatric ophthalmologists at the Emory Eye Center.

Currently, there are no validated questionnaires or tools to determine how children in these age groups cope with their visual impairments and the impact of vision loss on their daily lives. This knowledge can enhance physiciansâ€™ understanding of diseases that affect vision.

Emory Eye Center doctors Emily Graubart, MD, assistant professor of ophthalmology, and Paul Pruett, MD, assistant professor of ophthalmology, Emory School of Medicine, say people often have misinformation about their eyes. They answer questions below to dispel myths about eye disease and eye care. Start the new year with knowledge about your eyes:

Paul Pruett, MD

How often does an adult need to see an eye doctor?
â€œIt depends on your age,â€ says Pruett, an expert in glaucoma. â€œIn your 20s, 30s and 40s, about every two years is sufficient. If you have certain medical conditions, it may be necessary to be seen more often. For example, patients with diabetes should have their eyes examined every year, at the least. Many eye diseases can be asymptomatic, and early detection can prevent vision loss. This is especially true for glaucoma. Half of all patients with glaucoma do not know they have the disease.â€

Is my computer work damaging my eyes?
â€œNo, however, staring at a computer screen means you may not blink often and your eyes may become dry,” says Graubart, a comprehensive ophthalmologist and cataract surgeon. â€œBlinking more frequently while working on the computer, as well as using preservative-free artificial tears will help to reduce the dry-eye symptoms associated with long-term computer use.â€

Emily Graubart, MD

Do certain foods or vitamins help the eyes?
â€œWhile there are a lot of claims regarding vitamins and eye health, there are only a few conditions where studies have proven a benefit,â€ says Pruett. â€œIn age-related macular degeneration, for instance, there is a certain formulation of vitamins and minerals that has been proven to reduce the rate of vision loss in certain populations of these patients. Despite these medicines being over-the-counter, it is important to discuss with your doctor whether vitamin therapy is right for you as there may be potential interactions with other medicines or conditions. In general, a well-balanced diet with plenty of fruits and vegetables is the way to go, not only for eye health but also for your overall health.â€

Why does reading get more difficult with age?
â€œWe begin to lose our ability to focus up close, which is called presbyopia, between our late thirties and early forties,â€ says Graubart. â€œThe natural lenses of our eyes become thicker and harder, and the muscles controlling the lens shape weaken making it more difficult to see up close. If you have not needed glasses before, you will likely do well with over-the-counter reading glasses. These glasses cannot damage your eyes. However, the American Academy of Ophthalmology recommends a comprehensive eye exam at age 40 to screen for diseases of the eye. At this visit, your ophthalmologist can tell you what prescription would work best for your eyes.â€

Does reading in dim light or reading very small print damage your eyes?
â€œNo. You may experience eye strain with both of these activities, but there will be no permanent damage to your eyes,â€ says Graubart. â€œMore light helps to improve contrast and thus, allows you to read with greater ease.â€

Are eye problems genetic?
â€œNot always,â€ says Pruett. â€œAlthough there is a higher risk for certain diseases, such as glaucoma that run in families, it does not mean you as a child will get every eye disease or disorder that your parents may have had. Problems that come purely with aging, such as cataracts, have no relation to parents. The important thing to remember is that if you have a family history of eye disease, you need to have thorough screenings at appropriate times in your life.â€

Do eye exercises help vision?
â€œIn children with certain convergence issues (crossed eyes), the exercises prescribed for them do help,â€ says Pruett. â€œHowever, in adults, eye exercises have shown no improvement in vision according to studies. Methods that promise to get rid of glasses by eye exercises are not viable.â€

Does my toddler need an eye exam?
â€œYour childâ€™s eyes are examined as a newborn by your pediatrician, and then again between ages six months and one year.â€œ says Graubart. â€œYour childâ€™s vision should be tested by your pediatrician or an ophthalmologist at age three to three and one-half, earlier if your child can recognize images on the pediatric eye chart. If your child has a family history of eye disease, if you notice your childâ€™s eye wandering, or if you have any concerns regarding their vision, they should be screened regularly and quickly referred to an ophthalmologist if there are any concerns.â€

The patients seen by Emory low vision specialist Susan Primo, OD, MPH, have already exhausted most of their treatment options. They’ve completed medication regimens or had surgery to slow advanced age-related macular degeneration (AMD), a leading cause of blindness in the elderly. But still they don’t see well.

That’s where Primo comes in. At the Emory Eye Center, sheâ€™s studying whether behavioral modifications can lead to a change in brain activity to maximize use of remaining vision.

In macular degeneration, the maculaâ€”a layer of tissue on the inside back wall of the eyeballâ€”gradually deteriorates. That delicate tissue is responsible for visual acuity, particularly in the center of the retina. Central vision is needed for seeing small and vivid details such as words on a page or the color of a traffic light, which means it is vital for common daily tasks such as reading or driving.

In more than two decades of working with patients who are visually impaired, Primo realized that people typically use their peripheral vision to compensate for loss in central vision. Studies have shown that people with progressive central vision loss compensate by spontaneously adopting a preferred retinal location (PRL) that takes over responsibility for visual clarity.

Normal vision

But Primo and Georgia Tech psychologist Eric Schumacher wanted to know whether using these peripheral regions causes a change in how the brain is organized. Armed with Schumacher’s expertise in functional magnetic resonance imaging (fMRI) and Primo’s clinical experience, the researchers did indeed discover continued activity in the part of the brain that maps to the macula. The brain scans of people with AMD who had developed their peripheral vision showed substantially more activity than those of people who had not developed a PRL. Their study appeared in the December 2008 edition ofRestorative Neurology and Neuroscience.

In a current study, Primo and Schumacher are exploring whether occupational training and biofeedback can help people with AMD focus on using good retinal cells and in turn speed up the brain’s reorganization.

“Although others have tried to study this reorganization of macular degeneration before, no one, to our knowledge, has tried to influence it,” says Primo. “Yet it’s important to begin to come up with therapies, treatments, and technology to help patients begin to use their residual vision faster and better than they could before.â€